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Old 01-17-2020, 04:48 PM   #1
Bloopeta
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Default Bush LED40127FHDCNTD No Picture

Hi, I have a Bush LED40127FHDCNTD

The TV powers on, and backlights illuminate solid, for a few seconds, but no image is diplayed, and after a few seconds the backlights become dimmer, and flicker exceptionally fast, like a strove light effect. No image is ever displayed on the screen.

If I unplug the ribbon cable from mainboard to tcon/driver board, the backlights still act in the same strobe like manor, they do not stabilise

Any advice greatly appreciated
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Old 01-17-2020, 04:55 PM   #2
nomoresonys
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Default Re: Bush LED40127FHDCNTD No Picture

Seems like the usual backlight circuit issue, either bad connection or bad led/s.
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Old 01-17-2020, 04:56 PM   #3
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Default Re: Bush LED40127FHDCNTD No Picture

Quote:
Originally Posted by nomoresonys View Post
Seems like the usual backlight circuit issue, either bad connection or bad led/s.
Would that affect the no image problem also??
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Old 01-17-2020, 05:03 PM   #4
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Default Re: Bush LED40127FHDCNTD No Picture

Good question, maybe unplug the backlights at powerboard, look at the screen with a flashlight hit menu etc. see if you see any text or anything on screen.
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Old 01-17-2020, 05:10 PM   #5
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Default Re: Bush LED40127FHDCNTD No Picture

Quote:
Originally Posted by nomoresonys View Post
Good question, maybe unplug the backlights at powerboard, look at the screen with a flashlight hit menu etc. see if you see any text or anything on screen.
Ill give it a go.

Just Ive been reading through some old threads where people have described the flashing backlight issue, but they still had an image, and could navigate through menus etc, where as I get nothing.

Would there be any point illuminating the backlights with LED tester to see if they still flash? Or would that be pointless?
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Old 01-17-2020, 05:16 PM   #6
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Default Re: Bush LED40127FHDCNTD No Picture

The tester might tell you if you are getting the proper voltage from the leds.
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Old 01-17-2020, 05:23 PM   #7
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Default Re: Bush LED40127FHDCNTD No Picture

Quote:
Originally Posted by nomoresonys View Post
The tester might tell you if you are getting the proper voltage from the leds.
How would I go about testing using this plug with being 6 wires?
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Old 01-17-2020, 05:27 PM   #8
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Default Re: Bush LED40127FHDCNTD No Picture

Beside the flickering backlights, it should not affect the T-CON function to produce the image on the screen. Did you check to see if you do have 12VDC at both ends of the T-CON fuse with ref. to the chassis gnd?
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Old 01-17-2020, 05:32 PM   #9
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Default Re: Bush LED40127FHDCNTD No Picture

Quote:
Originally Posted by budm View Post
Beside the flickering backlights, it should not affect the T-CON function to produce the image on the screen. Did you check to see if you do have 12VDC at both ends of the T-CON fuse with ref. to the chassis gnd?
Yes m8 I did, steady 12.36v both sides

Dont know if its relevant, but there is what I would describe as a fluttering noise coming from the blue one on powerboard, I would say in sync with the flashing backlights
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Old 01-17-2020, 06:48 PM   #10
Bloopeta
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Default Re: Bush LED40127FHDCNTD No Picture

Again, not sure if this is relevant but when TV firsts starts up, the screen illuminates brighter as you would expect and lights are steady, but no image, then after a few secomds dims down, and you get the pulsating/strobing backlights, which, the strobing tbh isnt so visable looking at the screen, its more noticable as I have the back cover removed and can be seen through the holes in the chassis from the rear.

I have tried to capture it in a dark room in the following attached pictures. Please note the 1st pic, when the screen is bright and steady, its not multicoloured, its just the usual grey you would expect as normal, but for some reason my camera shows colours lol
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File Type: jpg 20200118_004014.jpg (130.9 KB, 4 views)
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Old 02-04-2020, 08:12 AM   #11
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Default Re: Bush LED40127FHDCNTD No Picture

I have stripped this down today, this is the first time I have came across a TV with backlight set up like this.

So all the backlights are lit, just with a strobe light effect. Have checked all the plugs and connections, no change.

What is the best way to go about testing these in the correct manor?
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Old 02-04-2020, 08:31 AM   #12
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Default Re: Bush LED40127FHDCNTD No Picture

Also, just having a look on the underside of the powerboard, and came across this bit, does that look strange to anyone? Or would that be normal???
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File Type: jpg 20200204_142751.jpg (631.4 KB, 4 views)
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Old 02-04-2020, 11:36 AM   #13
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Default Re: Bush LED40127FHDCNTD No Picture

Do these readings look ok?? Readings taken with TV turned on and backlights strobing

Backlight Plug

1. 86.1v fluctuates up to 88.2v and down to 80.7v
2. 17.1v
3. 16.7v
4. 80.7v fluctuates 80.9v
5. 23.8v fluctuates 24.0v
6. 16.7v fluctuates 16.8v


Plug to Mainboard

1. 24.9v
2. 0v
3. 0v
4. 0v
5. 03.01v
6. 0v
7. 00.6v
8. 0v
9. 05.5v
10. 12.4v
11. 05.5v
12. 05.3v
13. 12.8v
14. 12.4v
15. 25.1v
16. 03.3v
17. 03.4v
18. 03.3v
19. 0v
20. 0v
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File Type: jpg 20200204_162553.jpg (1.61 MB, 1 views)
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Old 02-06-2020, 04:45 AM   #14
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Default Re: Bush LED40127FHDCNTD No Picture

Anyone??
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Old 02-07-2020, 08:38 AM   #15
Bloopeta
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Default Re: Bush LED40127FHDCNTD No Picture

Also, when inspecting the tcon/driver board, this capacitor cd7 looks a bit dodgy
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